1. Field of the Invention
The present invention relates to a wiring board and a semiconductor device using the same as well as a method for manufacturing a wiring board.
2. Description of Related Art
Chip On Film (COF) is known as a package module using a tape wiring board. In the COF, a semiconductor chip is mounted on a flexible insulating tape wiring board, and the mounted portion is protected by encapsulating the semiconductor chip with a resin. The tape wiring board includes, as major elements, an insulating film substrate and a plurality of conductive wirings formed on a surface thereof. In general, the film substrate is made of polyimide, and the conductive wiring is made of copper. A metal plated coating or a solder resist film optionally is formed on the conductive wirings.
The COF mainly is used for the mounting of a driver for driving a display panel such as a liquid crystal panel. For instance, JP2004-327936 A describes an exemplary wiring board used in the COF. FIG. 8 shows an exemplary tape wiring board described in JP2004-327936 A, which is a plan view of a major region including a semiconductor mounting region of the tape wiring board. In FIG. 8, reference numeral 101 denotes an inner lead, 102 denotes a bump electrode and 103 denotes a semiconductor mounting region.
When a semiconductor chip is mounted on the thus configured wiring board, heat and pressure or ultrasonic vibration is applied thereto so as to bond electrodes (not illustrated) on the semiconductor chip with the bump electrodes 102. The bump electrodes 102 used for the bonding are manufactured by electrolytic plating or the like, and the thus manufactured bump electrodes generally tend to have varying heights. Conceivably, this results from a variation in a distance between a portion for an electrode to be formed and a current source or a variation in the width of the conductive wirings or the size of the bump electrodes. A variation in height of the bump electrodes 102 will cause a failure of some of the bump electrodes 102 to be bonded with the semiconductor chip, resulting in open defects.